Film forming apparatus, substrate for forming oxide thin film and production method thereof

ABSTRACT

The invention provides a film forming apparatus that is capable of forming films sequentially with two types of film forming mechanisms in the same chamber. The film forming apparatus according to the present invention includes a Pt target disposed at one side within a film forming chamber, a sputtering output mechanism to supply to the Pt target, a Pt vapor deposition source disposed at an other side within the film forming chamber, a vapor deposition output mechanism to supply to the Pt vapor deposition source, a substrate holder disposed between the Pt target and the Pt vapor deposition source within the film forming chamber to mount a substrate, a rotating mechanism to move the substrate holder so that the substrate directs to the Pt target or to the Pt vapor deposition source, a heating mechanism to heat the substrate when the substrate is subjected to a sputtering film forming, and a cooling mechanism to cool the substrate when the substrate is subjected to vapor deposition film forming.

This is a Continuation of application Ser. No. 10/376,594 filed Mar. 3,2003. The entire disclosure of the prior application is herebyincorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a film forming apparatus that iscapable of forming films sequentially with two types of film formingmechanisms in the same chamber. The present invention also relates to abase substrate to form an oxide thin film thereon, that is a substrateto form the oxide thin film on which the oxide thin film havingexcellent properties and electrical properties can be easily formed, andto a production method thereof.

A related art magnetron sputtering apparatus is described below.

The magnetron sputtering apparatus produces high density plasma on atarget by applying the magnetic field that intersects with the electricfield to subject a trochoid movement to electrons emitted from acathode. Thus, this sputtering apparatus has excellent powerefficiencies that can enhance a sputtering speed at a relatively lowvoltage.

A related art ion beam sputtering apparatus is described below.

The ion beam sputtering apparatus forms a film at a low gas pressure bytaking ion beams that are accelerated at high energy from an independention source, and by impinging the ion beams on a target under high vacuumatmosphere.

A related art electron beam heating vacuum vapor deposition apparatus isdescribed below.

The electron beam heating vacuum vapor deposition apparatus irradiates amaterial to be evaporated with electron beams, heats it and evaporatesit by utilizing an electron impact. In this method, a crucible iswater-cooled. Therefore, impurities within a material of the cruciblehave low possibility to contaminate a vapor deposition film, and amaterial having a high melting point, a semiconductor or an oxide can bevapor deposited.

In the above-mentioned related art sputtering apparatuses and the vapordeposition apparatus, when a first thin film is formed on the substrateby sputtering, and a second thin film is formed on the first thin filmto produce an oxide thin film forming substrate, the first thin film andthe second thin film cannot be formed sequentially. In other words, thesubstrate is introduced into a chamber of the sputtering apparatus, thefirst thin film is formed on the substrate by sputtering, the substrateis then taken out from the chamber, the substrate is introduced into achamber of the vapor deposition apparatus, and the second thin film isformed on the first thin film by a vapor deposition method. Accordingly,the first thin film and the second thin film cannot be formedsequentially within the same chamber.

As an example, a Pt substrate formed in a related art batch process isdescribed below.

A metal Pt material can change its structure depending on a formingtemperature. For example, when a Pt thin film is formed on a substrateat a temperature ranging from room temperature to not exceeding 300° C.,a very flat Pt substrate is formed. However, such a substrate has poorcrystallinity and orientation properties as compared with the one formedby heating at 300° C. or more. Accordingly, when an oxide thin filmforming solution is used to form an oxide thin film by a spin coatmethod and the like on the flat Pt substrate on which the Pt thin filmis formed at a temperature not exceeding 300° C., poor crystallinity andorientation properties of the Pt substrate may result in poorcrystallinity and orientation properties of the oxide thin film thereon,although the thin film is very easily formed.

On the other hand, when a Pt thin film is formed on the substrate at aforming temperature ranging from 300° C. to 650° C., the Pt thin filmhas a distinct columnar structure and its crystallinity (orientationproperties) is enhanced as the temperature increases. However, a gapwill be produced between Pt columns. If an oxide thin film is formed onsuch a Pt substrate, the oxide thin film forming solution itself oroxide thin film constituent elements will be dispersed between the Ptcolumns, and a composition of the oxide thin film especially at aninterface with the Pt substrate will have a distribution, although theoxide thin film can easily attain excellent crystallinity andorientation.

When the Pt thin film is formed on the substrate at 650° C. or more, thefilm is in a granulated structure. In this case, the Pt thin film willhave a surface with a poor morphology and poor orientation properties.Correspondingly, the oxide thin film thereon cannot be excellentlyproduced.

In addition, the following is commonly applied to all of theabove-mentioned Pt substrates. When the Pt thin film is formed by thesputtering method, a mechanism is used such that an inert gas or thelike is changed to be a high energy plasma, the Pt target is exposed tothe plasma and energy of the plasma is transferred to a Pt element ofthe Pt target, whereby the Pt thin film is coated on the substrate.Accordingly, the thus-formed Pt substrate contains a great amount of theinert gas. Typically, an argon (Ar) gas is often used, which results inthe Pt substrate on which a great amount of Ar is adsorbed. When theoxide thin film is formed on the Pt substrate, Ar is emitted from the Ptsubstrate to the oxide thin film in every thermal step. This might causepeeling at the interface, perforation or poor orientation properties.

SUMMARY OF THE INVENTION

The present invention addresses the above and/or other issues, andprovides a film forming apparatus being capable of forming filmssequentially with two types of film forming mechanisms in the samechamber. The present invention provides a substrate to form an oxidethin film, that is an oxide thin film forming substrate on which theoxide thin film having excellent properties can be easily formed. Theinvention also provides a production method thereof.

In order to address or solve the above, an apparatus to form a filmaccording to the present invention is provided that includes: a filmforming chamber, a substrate holder disposed within the film formingchamber to mount a substrate, a first film forming mechanism disposedwithin the film forming chamber to form a first electrode thin film onthe substrate, and a second film forming mechanism disposed within thefilm forming chamber to form a second electrode thin film on the firstelectrode thin film.

An apparatus to form a film according to the present invention includesa film forming chamber, a substrate holder disposed within the filmforming chamber to mount a substrate, a sputtering film formingmechanism disposed within the film forming chamber to form a firstelectrode thin film on the substrate by a sputtering, and a vapordeposition film forming mechanism disposed within the film formingchamber to form a second electrode thin film on the first electrode thinfilm by a vapor deposition method.

The above-mentioned film forming apparatuses include the sputtering filmforming mechanism and the vapor deposition film forming mechanism,whereby the film can be formed by the sputtering and the vapordeposition method. Using the film forming apparatuses, the firstelectrode thin film is formed on the substrate by the sputtering filmforming mechanism, and sequentially the second electrode thin film isformed on the first electrode thin film by the vapor deposition filmforming mechanism. Thus, the oxide thin film forming substrate can beproduced. The oxide thin film having excellent properties can be easilyformed on the oxide thin film forming substrate.

In the film forming apparatus according to the present invention, thefirst electrode thin film can be one selected from the group of a Ptelectrode thin film, an Ir electrode thin film and a Ru electrode thinfilm. The second electrode thin film can be one selected from the groupof a Pt electrode thin film, an Ir electrode thin film and a Ruelectrode thin film.

An apparatus to form a film according to the present invention includesan electrode target including of one of Pt, Ir and Ru disposed at oneside within a film forming chamber, a sputtering output mechanism tosupply to the electrode target, an electrode vapor deposition sourceincluding one of Pt, Ir and Ru disposed at the other side within thefilm forming chamber, a vapor deposition output mechanism to supply tothe electrode vapor deposition source, a substrate holder disposedbetween the electrode target and the electrode vapor deposition sourcewithin the film forming chamber to mount a substrate, a drivingmechanism to move the substrate holder so that the substrate directs tothe electrode target or to the electrode vapor deposition source, aheating mechanism to heat the substrate when the substrate is subjectedto a sputtering film forming, an oxidizing gas supplying mechanism tosupply an oxidizing gas to the film forming chamber, and a coolingmechanism to cool the substrate when the substrate is subjected to avapor deposition film forming.

The above-mentioned film forming apparatuses include the electrodetarget, the sputtering output mechanism, the electrode vapor depositionsource and the vapor deposition output mechanism, whereby the film canbe formed by the sputtering and the vapor deposition method. Using thefilm forming apparatuses, the first electrode thin film is formed on thesubstrate by the sputtering in the state that the substrate is heated tothe predetermined temperature by the heating mechanism, the substrate iscooled to the predetermined temperature by the cooling mechanism andsequentially the second electrode thin film is formed on the firstelectrode thin film by the vapor deposition film forming mechanism.Thus, the oxide thin film forming substrate can be produced. The oxidethin film having excellent properties can be easily formed on the oxidethin film forming substrate.

A film forming apparatus according to the present invention includes anelectrode target including one of Pt, Ir and Ru disposed at one sidewithin a film forming chamber, a sputtering output mechanism to supplyto the electrode target, an electrode vapor deposition source includingone of Pt, Ir and Ru disposed at one side within the film formingchamber, a vapor deposition output mechanism to supply to the electrodevapor deposition source, a substrate holder disposed at the other sidewithin the film forming chamber to mount a substrate, a heatingmechanism to heat the substrate when the substrate is subjected to asputtering film forming, an oxidizing gas supplying mechanism to supplyan oxidizing gas to the film forming chamber, and a cooling mechanism tocool the substrate when the substrate is subjected to a vapor depositionfilm forming.

A method of producing an oxide thin film forming substrate according tothe present invention includes forming a first electrode thin filmincluding one of Pt, Ir and Ru on a substrate at a substrate temperatureranging from room temperature to 650° C. by sputtering, and forming asecond electrode thin film including one of Pt, Ir and Ru on the firstelectrode thin film at substrate temperature not exceeding 350° C.

In the oxide thin film forming substrate formed by the above-mentionedproduction method, the second electrode thin film is sequentially vapordeposited at low temperature not exceeding 350° C. on the firstelectrode thin film having excellent crystallinity and orientationproperties formed by the high temperature sputtering from roomtemperature to about 650° C., thereby providing a dense and flat oxidethin film forming substrate having excellent crystallinity andorientation properties. In addition, since a significant or major partof the oxide thin film forming substrate is a low temperature vapordeposited film and Ar gas is only a little or slightly contained in thefilm, the Ar gas is hardly liberated later. Consequently, the oxide thinfilm having excellent properties can be easily formed on the oxide thinfilm forming substrate.

An oxide thin film forming substrate according to the present inventionincludes a substrate, a first electrode thin film including one of Pt,Ir and Ru formed on the substrate, and a second electrode thin filmincluding one of Pt, Ir and Ru formed on the first electrode thin film.The first electrode thin film is formed at a substrate temperatureranging from room temperature to 650° C. by sputtering. The secondelectrode thin film is formed at a substrate temperature not exceeding300° C. by a vapor deposition method.

An oxide thin film forming substrate according to the present inventionincludes a substrate, a first electrode thin film including one of Pt,Ir and Ru formed on the substrate, and a second electrode thin filmincluding one of Pt, Ir and Ru formed on the first electrode thin film.The first electrode thin film is formed at a substrate temperatureranging from room temperature to 650° C. by sputtering. The secondelectrode thin film is formed at a substrate temperature not exceeding300° C. by a vapor deposition method. A film thickness of the firstelectrode thin film is ⅕ or less of a film thickness of the secondelectrode thin film.

According to the above-mentioned oxide thin film forming substrate,since a significant or major part of the electrode thin film is thesecond electrode thin film, the second electrode thin film is a lowtemperature vapor deposited film and Ar gas is only a little or slightlycontained in the film, the Ar gas is hardly liberated later.Consequently, the oxide thin film having excellent properties can beeasily formed on the oxide thin film forming substrate.

As described above, according to one aspect of the present invention,the same chamber includes two types of the film forming mechanisms.Accordingly, there can be provided the film forming apparatus beingcapable of forming films sequentially with two types of film formingmechanisms in the same chamber. According to the other aspect of thepresent invention, there can be provided a substrate to form an oxidethin film, that is an oxide thin film forming substrate on which theoxide thin film having excellent properties can be easily formed, and aproduction method thereof.

In other words, using the film forming apparatus including the two typesof the film forming mechanisms within the same chamber, the secondelectrode thin film can be formed without taking out the substrate fromthe chamber after the first electrode thin film is formed. Since thefirst electrode thin film is not exposed to atmosphere, the surface ofthe first electrode thin film can be prevented from being contaminatedor the contamination can be reduced. When the second electrode thin filmis formed on the top of the first electrode thin film, the information,such as the crystallinity of the first electrode thin film, can beadvantageously transmitted to the second electrode thin film.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of the film forming apparatus according to a firstexemplary embodiment of the present invention;

FIG. 2 is a schematic of the film forming apparatus according to asecond exemplary embodiment of the present invention;

FIG. 3 is a sectional view of the oxide thin film forming substrate;

FIG. 4 is a graph showing ferroelectric hysteresis properties.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Exemplary embodiments of the present invention are described belowreferring to the figures.

FIG. 1 is a schematic of the film forming apparatus according to thefirst exemplary embodiment of the present invention. The film formingapparatus can form the film by the sputtering and the vapor depositionmethod.

As shown in FIG. 1, the film forming apparatus has a film formingchamber 1, and a Pt target electrode 2 is disposed at a top of the filmforming chamber 1. At a bottom of the film forming chamber 1, a Pt vapordeposition source 3 is disposed, and in the vicinity of a center of thefilm forming chamber 1, a substrate holder 4 is disposed.

The Pt target electrode 2 includes a Pt magnetron electrode 8, magnets9, a cathode electrode 10 and a Pt target 11. The Pt target 11 isdisposed facing to the substrate holder 4. To the magnetron electrode 8,a high frequency power supply (RF power supply) or a direct power supply(DC power supply) is connected.

The Pt vapor deposition source 3 includes a crucible containing a Ptevaporation material and an electron gun (EB gun) 12. To the crucible, acooling mechanism (not shown) is attached. The Pt vapor depositionsource 3 irradiates the Pt evaporation material with electron beams fromthe electron gun 12, heating it and evaporating Pt.

The substrate holder 4 holds the substrate 5, and is attached to arotating mechanism 6. The substrate holder 4 is rotated by the rotatingmechanism 6 to face the substrate to the Pt target electrode 2 and thePt vapor deposition source 3, respectively. The substrate holder 4 mayalso be rotated by any other rotating mechanism (not shown) in the statewhere it faces the Pt target electrode 2 and the Pt vapor depositionsource 3, respectively. At a top (an opposite side of a mounting side ofthe substrate 5) of the substrate holder 4, a heater (an infrared raylamp) 7 to heat the substrate is disposed. At a bottom surface (themounting side of the substrate) of the substrate holder 4, a reflector(not shown) is disposed. The substrate holder 4 also includes asubstrate cooling mechanism (not shown) to decrease a substratetemperature.

To the film forming chamber 1, a gas system (not shown) to supply asputtering inert gas and an exhaust pump system (not shown) to decreasean internal pressure in the film forming chamber 1 to the predeterminedpressure are connected.

A method of forming a thin film on a substrate using the film formingapparatus shown in FIG. 1 is described below. A final product producedusing the film forming apparatus is an oxide thin film formingsubstrate.

Firstly, the substrate 5 is mounted on the substrate holder 4 and thesubstrate holder 4 is rotated by the rotating mechanism 6 to face thesubstrate 5 to the Pt target 11. Then, the film forming chamber 1 isevacuated with the exhaust pump system so that the internal pressure inthe film forming chamber 1 reaches the predetermined pressure (forexample, about 1×10⁻⁶ Torr). Then, an inert gas (for example, Ar) issupplied to the film forming chamber 1 from the gas system so that theinternal pressure of the film forming chamber is maintained at thepredetermined pressure (for example, about 1×10⁻³ Torr to 1×10⁻² Torr).

The heater 7 is turned on to increase the substrate temperature to thepredetermined temperature (room temperature to about 650° C., preferablyabout 600° C.) and the substrate is maintained at the temperature.

The Pt target 11 is powered to sputter a surface of the Pt target 11with the inert gas. As a result, a first Pt thin film having a filmthickness of about 5 to 10 nm is deposited on the surface of thesubstrate 5 facing to the Pt target 11. Specifically, once the cathodeelectrode 10 is powered via the Pt magnetron electrode 8 in the Pttarget electrode 2 from the power source, discharge is produced betweenthe cathode electrode 10 and the substrate 5 to form plasma. The magnets9 form lines of magnetic force, whereby portions with high plasmadensity are formed near the surface of the Pt target. Sputter atomssputtered from the Pt target 11 are deposited on the substrate 5 to forma film on the substrate 5. Thus, a first Pt thin film having a filmthickness of about 5 to 10 nm is formed on the substrate 5.

Then, the power supply to the Pt target 11 is stopped to terminate thesputtering. The supply of the inert gas is also stopped. The infraredray heater 7 is also turned off.

Thereafter, the substrate holder 4 is rotated by the rotating mechanism6 to face the substrate 5 to the Pt vapor deposition source 3. Thesubstrate 5 is cooled by the substrate cooling mechanism to decrease thesubstrate temperature to 30° C. or less.

The Pt vapor deposition source 3 is powered to evaporate Pt and to vapordeposit it on the substrate 5. Thus, a second Pt thin film having a filmthickness of about 100 to 200 nm is deposited on the first Pt thin film.In order to enhance an in-plane film thickness distribution of thesecond Pt thin film, the substrate is rotated in-plane by the rotatingmechanism. Specifically, while the substrate is rotated in-plane, the Ptevaporation material is irradiated with the electron beams by theelectron gun 12 and is heated to evaporate Pt, whereby the second Ptthin film is formed on the first Pt thin film.

Then, the power supply to the Pt vapor deposition source 3 is stopped toterminate the vapor deposition. Thus, the oxide thin film formingsubstrate is produced.

FIG. 3 is a sectional view showing the oxide thin film forming substrateproduced as described above.

An oxide thin film forming substrate 13 includes the substrate 5. On thesubstrate 5, a first Pt thin film 14 having a thickness of about 5 to 10nm is formed by sputtering. On the first Pt thin film 14, a second Ptthin film 15 having a thickness of about 100 to 200 nm is formed by avapor deposition method.

According to the first exemplary embodiment described above, using thefilm forming apparatus that can form the film by the sputtering and thevapor deposition method, the first Pt thin film 14 is formed on thesubstrate 5 by the sputtering, and sequentially the second Pt thin film14 is formed on the first Pt thin film 14 by the vapor depositionmethod. Thus, the oxide thin film forming substrate 13 can be produced.The oxide thin film having excellent properties can be easily formed onthe oxide thin film forming substrate 13.

For example, the Pt coated substrate formed by the above-mentioned filmforming apparatus is described. The Pt is sequentially vapor depositedat low temperature on the Pt coated substrate having excellentcrystallinity and orientation properties formed by the high temperaturesputtering, resulting in a dense and flat Pt coated substrate havingexcellent crystallinity and orientation properties. In addition, since amajor part of the Pt coated substrate is a low temperature vapordeposited film and Ar gas is only a little or slightly contained in thefilm, the Ar gas is hardly liberated later.

The reason why the oxide thin film having excellent properties can beformed on the oxide thin film forming substrate 13 is demonstrated in athird exemplary embodiment.

Although the magnetron sputtering method is used in the above-mentionedfirst exemplary embodiment, any other sputtering methods including a DCsputtering method, an RF sputtering method and an ion beam sputteringmethod using a sputtering ion gun can be used.

Although the electron beam vapor deposition (EB vapor deposition) methodutilizing the electron beam is used in the above-mentioned firstexemplary embodiment, any other vapor deposition methods including aresistance heating method can be used.

Although the Pt target electrode 2 is disposed at the top within thefilm forming chamber 1 and the Pt vapor deposition source 3 is disposedat the bottom within the film forming chamber 1 in the above-mentionedfirst exemplary embodiment, the disposition is not limited thereto andany other depositions can be used as long as they include the drivingmechanism that moves the substrate so as to face the Pt target electrodeor the Pt vapor deposition.

FIG. 2 is a schematic of the film forming apparatus according to thesecond exemplary embodiment of the present invention. The same parts asthose in FIG. 1 are referenced with the same number, and only thedifferent parts are described below.

At the bottom of the film forming chamber 1, the Pt target 11 isdisposed, and the Pt target 11 is disposed at a target holder 16. Thetarget holder 16 is constructed to be rotated by a rotating mechanism17. In the film forming chamber 1, a sputtering ion gun 18 is disposedto power the Pt target 11. The sputtering ion gun 18 irradiates ionbeams that are accelerated at high energy and impinges the ion beams onthe Pt target 11 under high vacuum atmosphere.

At the bottom of the film forming chamber 1, the Pt vapor depositionsource 3 is disposed. At a lower part of the film forming chamber 1, anion gun for assistance 20 is disposed. The ion gun for assistance 20irradiates the ion beams upon the vapor deposition to the substrate andassists the vapor deposition to the substrate.

At the top of the film forming chamber 1, the substrate holder 4 isdisposed. The substrate holder 4 can be rotated by a rotating mechanism19 in the state where it faces the Pt target 11 and the Pt vapordeposition source 3.

Then, a method of forming a film on a substrate using the film formingapparatus shown in FIG. 2 is described below.

Firstly, the substrate 5 is mounted on the substrate holder 4. Then, thefilm forming chamber 1 is evacuated with the exhaust pump system so thatthe internal pressure in the film forming chamber 1 reaches thepredetermined pressure. An inert gas (for example, Ar) is supplied tothe film forming chamber 1 from the gas system so that the internalpressure of the film forming chamber is maintained at the predeterminedpressure.

The heater 7 is turned on to increase the substrate temperature to thepredetermined temperature (preferably about 600° C.) and the substrateis maintained at the temperature.

The Pt target 11 is powered to sputter a surface of the Pt target 11with the ion beams. As a result, a first Pt thin film having a filmthickness of about 5 to 10 nm is deposited on the surface of thesubstrate 5 facing to the Pt target 11. Specifically, the ion beams thatare accelerated at high energy are taken out from the sputtering ion gun18 and are impinged on the Pt target 11 to form a first Pt film on thesubstrate.

Then, the power supply to the Pt target 11 is stopped to terminate thesputtering. The supply of the inert gas is also stopped. The infraredray heater 7 is also turned off.

Thereafter, the substrate 5 is cooled by the substrate cooling mechanismto decrease the substrate temperature to 200° C. or less.

The Pt vapor deposition source 3 is powered to evaporate Pt and to vapordeposit it on the substrate 5. Thus, a second Pt thin film having a filmthickness of about 100 to 200 nm is deposited on the first Pt thin film.In order to enhance an in-plane film thickness distribution of thesecond Pt thin film, the substrate 5 is rotated in-plane by the rotatingmechanism 19. Specifically, while the substrate 5 is rotated in-plane,the Pt evaporation material is irradiated with the electron beams by theelectron gun 12 and is heated to evaporate Pt, whereby the second Ptthin film is formed on the first Pt thin film. At this time, the ionbeams for assistance are irradiated by the ion gun for assistance,thereby assisting the film formation of the second Pt thin film.

Then, the power supply to the Pt vapor deposition source 3 is stopped toterminate the vapor deposition. Thus, the oxide thin film formingsubstrate is produced. Thus-produced oxide thin film forming substrateis the same as shown in FIG. 3.

In the above-mentioned second exemplary embodiment, the same advantagesas the first exemplary embodiment can be provided.

In the above-mentioned second exemplary embodiment, although the ionbeam sputtering method is used, any other sputtering methods can beused.

In the above-mentioned second exemplary embodiment, although theelectron beam vapor deposition (EB vapor deposition) method utilizingthe electron beam is used, any other vapor deposition methods can beused.

The third exemplary embodiment is described below.

Using the apparatus comprising the sputtering film forming mechanismsand the vapor deposition film forming mechanism according to the presentinvention used in the first exemplary embodiment, the following threeoxide thin film forming substrates were produced.

-   -   (1) Pt (190 nm, formed at room temperature)/Pt (10 nm, formed at        600° C.)/SiO₂ (200 nm)/Si substrate according to the present        invention    -   (2) Pt (200 nm)/Ti (20 nm)/SiO₂ (200 nm)/Si substrate produced        in the related art at room temperature; and    -   (3) Pt (200 nm)/Ti (20 nm)/SiO₂ (200 nm)/Si substrate produced        in the related art at 600° C.

The crystallinity and orientation properties of the Pt thin films formedwere determined by X-ray diffraction. As a result, the substrates (1)and (3) had similar peak intensity of Pt (111). The substrate (2) hadabout ¾ peak intensity of that of the substrate (1) or (3). In addition,in the substrates (1) and (3), only the peak of Pt (111) was detected.However, in the substrate (2), the peak of Pt (200) was also detected atthe same time. It can be concluded that the conventional Pt substrate(2) is poor as compared with the Pt substrate (1) according to thepresent invention and the related art Pt substrate (3).

Using the above-mentioned three substrates, the same ferroelectric thinfilms were formed on the top under the same film forming conditions. Thefilm forming conditions were as follows: (Film forming conditions)Ferroelectric Bi₄Ti₃O₁₂ Film forming method spin coat method Number ofrevolutions 4000 Temporary firing temperature 400° C. Crystallizationtemperature 650° C. Film thickness 100 nm

After the above-mentioned ferroelectric thin films were formed onrespective Pt coated oxide thin film forming substrates, and top Ptelectrodes each having a diameter of 100 μmΦ and a film thickness of 100nm were formed on the tops of the ferroelectric thin films at roomtemperature by the vapor deposition method, ferroelectric hysteresisproperties were determined. As a result, the hysteresis properties wereobtained as shown in FIG. 4.

Excellent ferroelectric properties were obtained only on theferroelectric thin film of the substrate (1). The substrate (2) hadabout ¾ ferroelectric properties of those of the ferroelectric thin filmof the substrate (1) as represented by remanence values. It was revealedthat this corresponded to XRD peak intensity of the Pt electrode. Inother words, the crystallinity and the orientation properties of theoxide thin film largely depend on the crystallinity and the orientationproperties of the Pt electrode, which determine electric properties ofthe oxide thin film. The ferroelectric thin film on the substrate (3)had great leak current, and therefore no ferroelectric hysteresis couldbe detected. In the substrate (3), the Pt itself had excellentcrystallinity and orientation properties similar to those of thesubstrate (1). However, the Pt electrode thin film was formed only at600° C. and had a columnar structure with low density. In addition, itwas revealed that a great amount of the argon (Ar) gas used in thesputtering was adsorbed on the Pt substrate, and it was released fromthe Pt upon the formation of the ferroelectric thin film. A number ofholes were observed on the surface of the ferroelectric thin film. It isconsidered that the holes were formed by the above-mentioned fact.Accordingly, the ferroelectric thin film on the substrate (3) had greatleak current, and therefore no ferroelectric hysteresis could bedetected.

Advantages of the Pt coated substrate formed, for example, by theproduction method of the present invention are described below. The Ptcoated substrate having excellent crystallinity and orientationproperties is formed by the high temperature sputtering method, and Ptis sequentially vapor-deposited thereon at low temperature, wherebyexcellent crystallinity and orientation properties of the hightemperature sputter Pt are also provided to the low temperature formedPt. The low temperature formed Pt keeps an original dense and flatsurface morphology. Accordingly, the dense and flat Pt coated substratehaving excellent crystallinity and orientation properties can be formed.In addition, since a major part of the Pt coated substrate is a lowtemperature vapor deposited film and Ar gas is little contained in thefilm, liberation of the Ar gas after various thermal treatments can beadvantageously reduced or prevented.

This invention is not to be unduly limited to the illustrative exemplaryembodiments set forth herein, and various modifications and alterationscan be made.

1. A method of producing an oxide thin film forming substrate,comprising: forming a first electrode thin film including at least oneof Pt, Ir and Ru on a substrate at a substrate temperature ranging fromroom temperature to 650° C. by sputtering; heating the substrate whenthe substrate is subjected to sputtering film forming; forming a secondelectrode thin film including at least one of Pt, Ir and Ru on the firstelectrode thin film at substrate temperature not exceeding 350° C. byvapor deposition; and cooling the substrate when the substrate issubjected to vapor deposition film forming.